Magnetic reversible nut



HWI!! Feb. 25, 1958 l.. K. DAvls 2,824,460

MAGNETIC REVERSIBLE NUT Filed Nov. 24, 1954 2 sheets-sheet 1 mur um 22 I CONTROL VENT f`|l5 UNCOLN K, DAvls 1' @il QM AGENT Feb. 25, 1958 L. K. DAVIS MAGNETIC REVERSIBLE NUT 2 Sheets-Sheet 2 Filed NOV. 24, 1954 CONTROL 1NVENToR.-

LINCOLN K. DAVlS United States Patent O MAGNETIC REVERSIBLE NUT Lincoln. K. Davis, Brockton, Mass., assignor to The Foxboro Company, Foxboro, Mass., a corporation of Massachusetts Application November 24, 1954, Serial No. 470,966

1, Claim. (Cl. 74.424,.8)

This invention relates to devices for translating movement of one body into movement of another body, and has particular reference to such devices wherein aY magnetically solidiable mass of discrete particles is used as,v the movement translation connection between the bodies.

This invention is concerned with providing the other body with a location-changing bodily movement. For example, an embodiment of this invention comprises a screw threaded shaft which is rotatably mounted and driven about its longitudinal axis, and which is fixed against lengthwise movement, with a housing movable along the screw shaft by means of a connection medium in the form of a magnetic particle mass in the housing and about the shaft, when the magnetic mass is solidi,- fred by the application of a magnetic iield thereto.

Industrial instruments such as indicators, recorders and controllers have movement structures to which this invention may be applied to advantage. For example: the mechanical valve stem movement involved in operating a tiow pipe valve may be controlled by electrical signals as applied to a device according to this invention.

It is an object of this invention to provide a new and improved magnetic movement translation device.

Other objects and advantages of this invention will be in part apparent and in part pointed out hereinafter, and in the accompanying drawings, wherein:

Figure I is a schematic and sectional showing of an embodiment of the present invention in a valve contro structure;

Figure Il illustrates an indicating structure embodying the present invention and utilizing, for the most part, the structure of Figure I;

Figure lll is a central axis cross-section of an alternate structure as an embodiment of the present invention;

Figures iV-Vi inclusive represent another alternate structure, respectively with a plan view, a transverse section on line V-V of Figure lV, and a fragmentary side view thereof; and

Figure VH is a schematic showing of another alternate structure.

Referring generally to Figure l, which will be detailed hereinafter, a screw shaft 16 is mounted for rotation in a housing 11. in turn, the housing 11 is mounted for sliding movement along the screw shaft 10. In the housing 11 and about the screw shaft 10, a body of magnetic particles 12 is provided, and a pair of magnetic coils 13 and 14 are mounted on the housing 11 about the screw shaft iti and about the body of magnetic particles 12. The screw shaft 1t) is provided with a left hand thread portion iti and a right hand thread portion The coils 13 and 14 are used to selectively apply a magnetic field to the portions of the body of magnetic particles (12) which are adjacent the screw thread portions 10 and itl, for the purpose of locally solidifying the selected portions of the magnetic particle body. As a result a matching and meshed thread, with respect to the selected screw thread portion, 10 or 10 is effectively formed in the magnetic particle body, and continued` 2,824,460 Patented 'F eb. Z5, 1958 ice rotation of the screw shaft 10 thereafter results in traveling nut movement of the housing 11 in one direction or the other along the screw shaft 10. A suitable con trol unit 15 is provided with electrical connections 16 and 17 through which the magnetic coils 13 and 14 may b e; selectively energized, for example,k in response to the changing values of a varying process condition such as temperature, tiow, etc.

The magnetic body 12 may be a dry mass of iron or iron composition microscopic particles. The particles arel magnetically soft, that is, they do not retain magnetic properties to any practical extent. Accordingly when no magnetic field is applied .to the magnetic body 12 itrcomprises only a mass of loose particles,l and the screw shaft 10 rotates therein with no movement produced in the housing 11. However, when a magnetic field is applied, the magnetic particles arrange themselves inv chains along flux lines, the mass becomes solidified, and movement of the housing 11 is produced.

Another form of the magnetic body 12 is as a magnetic tiuid mixture, usually with an oil as a fluid. This mixture is formed with millions of microscopic iron particles in suspension in a fairly light oil such as dash-pot silicone oil which has low vapor pressure characteristics and stable viscosity with respect to temperature changes. lt is desirable to relate the particle size and composition to the oil composition and weight with a View to providing a suspension factor which will keep the particles sus. pended and distributed in the oil for a relatively extended period of time. When unmagnetized, the particles are in dispersed condition and float freely in the oil. When a magnetic eld is passed through the mixture, the ironr particles become strongly attached to each other and bind the oil into a dense homogenous gel which might be called magnetic mud Since the viscosity of a body may be considered as the resistance of the molecules thereof to being pushed past each other, we may describe this action as magnetic viscosity providing soliditication. The mixture thickens suddenly into atough semisolid. The forces produceable in this arrangement are variable, not simply full on-full off. The oil vehicle provides an advantage in instances where it-is desirable to disperse heat of friction, etc. through or from the mixture.

The lower end of the Figure I housing 11 is in the form of a valve stem 18 which isoperated as the housing 11 is moved along the screw shaft 10, to open or close a flow passage 19 in a valve block 20.

The detail of Figure I includes a motor 21 with a drive shaft 22 secured in end to end axial alignment with the screw shaft 10 by a sleeve 23 and transverse pins 24. Thus, during the operation of this device, the screw shaft 10 is continuously rotated by the motor 21. The screw shaft 16 has smooth cylindrical formation at the top and bottom ends as shown in Figure I, and in its central portion, between the left and right hand thread portions 10' and 10". The movable housing 11 is cylindrical and concentric with the screw shaft 10, with housing end portions 25 and 26 apertured with the ends of the screw shaft 10 extending through these apertures. The housing end portions 25 and 26 are provided with screw shaft bearingl and sealing washers 25' and 26' of suitable rubber or plastic. The housing 11 has an inner chamber 27 which is cylindrical and concentric with the shaft 10, with this inner chamber encompassing both the left and right hand thread portions 10 and 10" of the screw shaft 10. The inner chamber 27 is substantially filled with the body of magnetic particles 12. The housing 11 is further provided with a pair of end to end outer annular chambers 2S for receiving the magneti-c coils 13 and 14.

As mentioned hereinbefore, the body O f magnetic particles 12 has the characteristic of becoming solidified when a magnetic field is applied thereto. Thus, when the magnetic particles around the right hand thread have a magnetic field applied thereto by the coil 13, those particles are magnetically joined and naturally conform to the inner wall shape of their container. Since the screw threads 10 and 10" form inner wall portions of the magnetic particle container, the solidication of the magnetic particles effectively forms a screw thread which is matched and meshed with the shaft thread 10". As a result the whole housing 11 and the body of magnetic particles 12 form a nut on the screw thread 10". At the left of Figure 1 the housing 11 is provided with an integral tongue 29 which extends laterally to terminate in a vertical slot 30 in a fixed block 31. Consequently the housing nut is held against rotation and the continued rotation of the screw shaft 10 causes the housing nut assembly to be moved along the screw shaft 10. In this case therefore, with the screw shaft 10 rotated clockwise as viewed from its lower end, and when the coil 13 is energized, the housing nut assembly is moved downward in the closing off direction with respect to the ow passage 19.

' Similarly, when the coil 14 is energized, the magnetic particles about the thread 10' are solidified to effectively form a matching thread, and the housing nut assembly is moved upward (Figure I) on the screw shaft 10. Consequently the flow passage 19 is opened as the valve stem 18 is lifted therefrom. When the coils 13 and 14 are simultaneously energized, the housing nut assembly is locked on the screw shaft 10, as far as longitudinal movement is concerned.

Figure II illustrates another use of the present invention in that the structure of Figure I is associated with a recording pen 32 and a rotatable record chart 33. The lower end of the housing 11 is a shaft 13 instead of the Figure I valve stem 18, and a mechanical connection 34 is provided between the shaft 18 and the recording pen 32. Thus the movement of the housing 11V produces movement of the recording pen 32 about a pivot 35 to provide a record on the chart 33. The record thus produced is in predetermined representative relation to electrical control signals which are applied to the device from the control unit and through the electrical leads 16 and 17.

Figure III illustrates a device embodying the present invention, wherein a driven threaded shaft 36 is provided with right and left hand thread portions 37 and 3S. A housing unit 39V contains the threaded portions of the shaft 36 and forms a chamber 40 in which a magnetic mixture 41 is contained in surrounding relation with the shaft threaded portions 37 and 38. The housing unit 39 comprises a pair of telescoping and open ended sleeves 42 and 43. The sleeve 43 has an enlarged outer diameter portion 44 forming one end of the housing unit 39 and is provided with a sealing and bearing plastic or rubber O ring 45 for engaging one end portion of the threaded shaft 36.

The sleeve 43, with a reduced outer diameter portion 46, forms the inner portion of the telescoping assembly, the portion 46 being sufficiently extended to enclose both of the shaft threaded portions 37 and Y315. The sleeve 42 has a portion 47 forming the other end of the housing unit 39, with a sealing and bearing G ring 48 therein and in engagement with the other end portion of the threaded shaft 36. The portion 47 of the sleeve 42 has an inner annular abutment against which the inner end of the sleeve 43 is seated. The remainder 49 of the sleeve 42 encompasses the portion 46 of the sleeve 43, with an O ring 50 provided as a seal therebetween. Further, the remainder 49 of the sleeve 42 is made up of two annular magnetic coils 51 and 52 which respectively encompass the shaft threaded portions 37 and 38, and an annular spacer 53 between the coils 51 and S2. As in Figures I and II, thelunit of Figure III is provided with a laterally extending arm 54, arranged in a slot SS in a fixed block 56 to prevent rotation of the housing unit 39 while at the same time allowing movement of the housing unit along the threaded shaft 36. In the present instance the arm 54 is secured to the annular spacer 53. The telescoping assembly is sufficiently tightly joined to form an integral housing unit with respect to such rotation.

The structure of Figure III is also provided with a feedback pipe 57 which extends from one end of the housing chamber 4t) to the other end thereof. This pipe is a relief passage for the magnetic mixture when it is undesirably pressured within the chamber 46 by the movement of the housing unit 39 along the threaded shaft 36. Preferably, the feedback pipe 57 is spaced from the magnetic coils 51 and 52 suiciently to prevent solidiiication of the magnetic fluid in the pipe 57, as a means of assuring easy feedback action.

' The Figure III device is provided with the usual control unit 58, and with electrical leads 59 and 60 there from to the magnetic coils 51 and 52. In this structure, the threaded shaft 36 is driven in rotation, and the housing unit 39 is movable therealong as indicated by the arrows 61 and according to the magnetic uid action as described hereinbefore in connection with Figure I. Suitable movement take-oif (not shown) may be applied to the housing unit 39, for example, in the manner and for the purposes illustrated in Figures I and II.

The alternate structure illustrated in Figures IV-VI comprises a housing unit 61 and a shafted unit 62. The housing unit 61 includes a supporting frame 63 with a rectangular tank 64 therein and a pair of parallel guide bars 65, one on each side of the tank 64 and extending lengthwise thereof. A sleeve 66 is slidably mounted on each of the guide bars 65, with a bridge-like magnetic coil structure 67 secured to the sleeves 66 so that the coil structure 67 is movable lengthwise with respect to the tank 64. Thus the coil structure 67 bridges the tank 64, and is provided with a pair of magnetic coils 68 and 69 which are side by side on a line transversely of the tank 64, with each coil overlying a different portion of the tank. The magnetic coils 68 and 69 are each provided (Figure V) with a pair of depending pole pieces 68 and 69 which extend into the tank 64. Each pole piece, at its lower end, has a laterally facing cylindrically curved surface such that the curved surfaces of each pair of pole pieces generally denes a cylinder within the tank 64 and parallel to the guide bars 65. A pair of parallel screw shafts 70, 71, is mounted in the tank 64, with the shafts respectively concentric and axially aligned with respect to the cylinders defined, as described above, by the magnetic coil pole pieces 68 and 69. Further, the tank 64 contains a body of magnetic fluid 72, with the form and characteristics described hereinbefore in connection with Figure I. It is preferable for the magnetic uid to be deep enough to cover and surround both the screw shafts 70, 71, and the cylindrical surfaces of the magnetic coil pole pieces 68', 69. However, for the purpose of illustration, the magnetic fluid in Figures IV and V is shown as'only partly encompassing the screw shafts 70, 71. Accordingly, the nature and arrangement of the screw shafts 71), 71 is clearly illustrated in Figure 1V. The tank 64 may be provided with a top cover (not shown) if desired. Preferably the tank is not completely filled with the magnetic mixture, thus providing top room for the mixture to move about in pressure equalizing action similar to that provided for by the Figure III feedback pipe 57.

The shafted unit 62 as indicated in Figure IV includes the screw shafts V70, 71, which are both provided with right hand thread portions within the compass of their respective magnetic coil pole piece pairs. The screw shafts 70, 71 are journaled in the end walls of the magnetic mixture tank 64 and are driven in rotation by a motor 73 through a gear train comprising a pinion 74,

a gear 75, on theend of the screw shaft 70, and a gear' 76 on the end of the screw shaft 71. Thus, while both screw shafts are provided with a right hand thread, one shaft is rotated clockwise and the other is rotated counter'- clockwise. Consequently when one magnetic coil is energized, magnetic fluid around its associated screw shaft is solidified, and the magnetic coil structure 67 is moved along the guide bars 65 in one direction. Similarly, the coil structure 67 is moved in the opposite direction when the other magnetic coil is energized. In this case also, suitable movement take-off (not shown) may be applied to the coil structure 67, in the manner and for the purposes illustrated in Figures I and II with respect to movement take-off from the housing 11.

The Figure VII simple schematic showing of a still further alternate structure illustrates a pair of pulleys 77 and 78 with a travelling ribbon 79 mounted thereon. The pulley 77 is driven from a pinion 80 through a gear 81, and the ribbon 79 is consequently continuously travelled over the pulleys 77 and 78 during the operation of the device in the directions indicated by the arrows 82. A double housing unit 83 is arranged for operative association with the ribbon 79, with an upper housing 84 and a lower housing 85. The upper housing 84 has a chamber 86 therein containing a body 87 of magnetic fluid through which the ribbon 79 is passed in its upper, left to right travel, and the lower housing 85A has a chamber 88 therein containing a body 89 of magnetic uid through which the ribbon 79 is passed in its lower, right to left travel. The upper housing 84 is surrounded by a magnetic coil 90, and the lower housing 85 is surrounded by a magnetic coil 91. Ribbon passage openings are provided in the ends of the upper and lower housings 84 and 85, with a plastic or rubber seal and wiper member 92 provided in each of these ribbon passage openings.

The double housing unit may be locked to the ribbon 79 for travel therewith by energizing one or the other of the magnetic coils 90, 91. The solidification of the magnetic fluid effectively locks the ribbon and housing unit together so that the ribbon travel movement is translated into housing unit movement. Suitable movement take-olf (not shown) may be applied to the double housing unit to produce a working movement as an output in predetermined relation to electrical signals as applied to the magnetic coils.

This invention, therefore, provides an improved magnetic movement translation device.

As many embodiments may be made of the above invention, and as changes may be made in the embodiments set forth above without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative only and not in a limiting sense.

I claim:

For use in an industrial instrument as a means of operating a iiow control valve, a magnetic clutch movement translation device comprising a rotatably driven screw shaft which has a left hand sharp V thread portion and a right hand sharp V thread portion thereon, a tubular sleeve chamber mounted on said shaft for movement therealong, and enclosing said left and right hand thread portions, said sleeve having an inner diameter substantially greater than the diameter of said shaft and said threaded portions thereof, said shaft having the same diameter throughout said chamber except for said screw thread portions, said threaded portions having equal major diameters somewhat greater than the diameter of said shaft, with said threaded portions thus providing the only abutments extending transversely of said shaft, a pair of magnetic coils wound on said sleeve, in integral relation thereon for movement therewith along said shaft, a magnetic particle mass in said chamber and about both of said left and right hand thread portions thus filling the said substantially greater inner diameter of said sleeve to provide relatively large radial thickness dimension in said particle mass between said shaft and said sleeve sufficient to provide a substantial "nut body of said particle mass whereby said magnetic coils, said sleeve, and said nut body move as a unit along said shaft as a nut along a bolt when said coils are energized and said shaft is rotating, means responsive to a control signal for selectively energizing said coils and applying a magnetic eld, in representation of said signal, locally to the said magnetic particle mass in the ambiences of said left and right hand threads to solidify said mixture at one of said threads and in effect to produce a screw thread formation in said solidified mixture to form said coils, said sleeve and a portion of said mixture into a single nut unit, whereby movement forces of said screw are applied to said chamber unit to produce movement of said shaft through said mixture in a predetermined direction according to which of said screw threads is associated with said solidified mixture, and a magnetic fluid mixture feedback passage extending from one end of the chamber of said unit to the other as a means of by-passing slippage portions of said mixture, said passage being located outside of the effective area of said magnetic eld, and whereby a ilow control valve stem may be secured to said chamber unit assembly for movement thereby as a means of opening v and closing a flow passage.

References Cited in the file of this patent UNITED STATES PATENTS 2,661,596 Winslow Dec. 8, 1953 2,720,819 Ryan Oct. 18, 1955 2,738,684 Shafer Mar. 20, 1956 FOREIGN PATENTS 295,771 Switzerland Ian. 15, 1954 976,917 France Mar. 23, 1951 

